1. Technical Field
The present disclosure relates to material storage containers and, specifically, to drain fittings for material storage containers.
2. Description of the Related Art
Bulk storage containers are commonly utilized for storage and dispensing of flowable materials. In some larger bulk storage containers, a valve may be located near the bottom of the container in order to facilitate controlled, gravity-driven dispensing of the flowable material though the valve, so that the container can be drained without a pump, and with no tilting or moving of the container.
One method of ensuring that substantially all of the flowable material contained within a bulk storage container is dispensable via gravitational forces is to position the tank outlet at the bottom-most portion of the storage tank wall. This “full drain” tank outlet is located adjacent to the bottom of a storage tank, and enables complete drainage of the tank. Full-drain outlets also facilitate “clean in place” procedures in which the tank is thoroughly cleaned at its service location, such as to remove heavy solids or salts that may accumulate at the bottom of the tank during use. Design efforts have focused on allowing clean in place procedures to be accomplished with minimal effort, preferably without the need for a worker to enter the interior of the storage tank being cleaned. Clean in place procedures are particularly useful where tanks must be cleaned between every fill, such as in the pharmaceutical and food industries.
Some bulk storage containers have full drain outlets integrally formed into the wall of the storage container. For example, polymer storage tanks may be manufactured to include an outwardly extending tube or channel at the bottom portion of the tank, which may then be connected to a tank valve to control the flow of flowable material through the tank outlet. However, the location of the integrally formed outlet extension at the bottom of the storage tank renders the outlet extension vulnerable to impact. For example, tank outlet extensions frequently include a flange extending downwardly past the bottom surface of the storage tank, which may be damaged if the tank is placed on a flat surface, i.e., before or during installation at a service site. If a tank outlet extension that is integrally molded or formed into a bulk storage container is damaged, the difficulty of repairing or replacing the integral tank outlet extension may render the tank unusable.
Other bulk storage containers feature removable tank outlet adapters which can be engaged with the wall of a bulk storage container. For example, as shown in FIG. 1, bulk storage container 1 includes an aperture 2 through a wall 3 thereof at a bottom portion of container 1. A threaded insert 4 may be embedded within wall 3 of container 1 to facilitate threaded engagement of an adapter 5 with wall 3. Typically, adapter 5 is made of a polymeric material, such as polyvinyl chloride (PVC) that is resistant to degradation from contact with chemicals or other materials which may be contained within storage container 1. On the other hand, threaded insert 4 is typically made of a metallic material to facilitate a tight engagement between the threads of adapter 5 and threaded insert 4.
However, the polymeric threads of adapter 5 are vulnerable to damage by engagement with the metallic threads of insert 4, such as by overtightening or removal and reinstallation. To minimize leakage of flowable material past a damaged threaded engagement, O-ring 6 is provided at the junction between adapter 5 and tank wall 3. O-ring 6 is also intended to prevent flowable material from engaging with, and potentially chemically degrading, threaded insert 4. In addition, a second O-ring 7 may be provided between adapter 5 and the exterior of tank wall 3 so that, if any flowable material does pass by O-ring 6 and threads 4, 5, leakage of the flowable material may be stemmed by second O-ring 7. However, if flowable material reaches second O-ring 7, the flowable material may attack the metallic material of threaded insert 4 and eventually cause degradation thereof.